Erythropoietin (Epo) is a substance that is normally made by the kidneys and stimulates the production of red blood cells. It is usually given to patients to treat anemia. Scientists recently discovered that Epo also is made in the brain after injury. In animal models of TBI, the brain's production of Epo has numerous protective effects, including reducing inflammation in the brain, reducing death of brain cells, and improving blood flow to the brain. In the laboratory, the effects of this naturally-occurring, protective agent can be enhanced by giving additional amounts intravenously. Because Epo may have beneficial effects for both the injured brain and anemia, scientists are studying the effects of giving Epo to patients with severe TBI.